/*    $OpenBSD: michael.c,v 1.2 2008/07/21 19:52:45 damien Exp $    */

/*
 * Copyright (c) 2005, 2006 Reyk Floeter <reyk@openbsd.org>
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

/*
 * Implementation of the Michael MIC as defined in IEEE 802.11i for TKIP.
 * The MIC generates a 64bit digest, which shouldn't be used for any other
 * applications except TKIP.
 */

#include <sys/param.h>
#include <sys/systm.h>

#include <crypto/michael.h>

#define ROL(n, x)    (((x) << (n)) | ((x) >> (32 - (n))))
#define ROR(n, x)    (((x) >> (n)) | ((x) << (32 - (n))))
#define XSWAP(x)    (((x) & 0xff00ff00UL) >> 8 | ((x) & 0x00ff00ffUL) << 8)

#if defined(__STRICT_ALIGNMENT) || _BYTE_ORDER != _LITTLE_ENDIAN
#define GETLE32(x)    ((x)[0] | (x)[1] << 8 | (x)[2] << 16 | (x)[3] << 24)
#define PUTLE32(x, v)    ((x)[0] = (u_int8_t)(v),            \
(x)[1] = (u_int8_t)((v) >> 8),            \
(x)[2] = (u_int8_t)((v) >> 16),        \
(x)[3] = (u_int8_t)((v) >> 24))
#else
#define GETLE32(x)    (*((u_int32_t *)(x)))
#define PUTLE32(x, v)    (*((u_int32_t *)(x)) = (v))
#endif

#define MICHAEL_BLOCK(l, r) do {                    \
r ^= ROL(17, l);                        \
l += r;                                \
r ^= XSWAP(l);                            \
l += r;                                \
r ^= ROL(3, l);                            \
l += r;                                \
r ^= ROR(2, l);                            \
l += r;                                \
} while (0)

void
michael_init(MICHAEL_CTX *ctx)
{
    bzero(ctx, sizeof(MICHAEL_CTX));
}

void
michael_update(MICHAEL_CTX *ctx, const u_int8_t *data, u_int len)
{
    int i;
    
    for (i = 0; i < len; i++) {
        ctx->michael_state |= data[i] << (ctx->michael_count << 3);
        ctx->michael_count++;
        
        if (ctx->michael_count >= MICHAEL_RAW_BLOCK_LENGTH) {
            ctx->michael_l ^= ctx->michael_state;
            MICHAEL_BLOCK(ctx->michael_l, ctx->michael_r);
            ctx->michael_state = ctx->michael_count = 0;
        }
    }
}

void
michael_final(u_int8_t digest[MICHAEL_DIGEST_LENGTH], MICHAEL_CTX *ctx)
{
    static const u_int8_t pad[] =
    { 0x5a, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 };
    
    michael_update(ctx, pad, sizeof(pad));
    
    PUTLE32(digest, ctx->michael_l);
    PUTLE32(digest + MICHAEL_RAW_BLOCK_LENGTH, ctx->michael_r);
}

void
michael_key(const u_int8_t *key, MICHAEL_CTX *ctx)
{
    ctx->michael_l = ctx->michael_key[0] =
    GETLE32(key);
    ctx->michael_r = ctx->michael_key[1] =
    GETLE32(key + MICHAEL_RAW_BLOCK_LENGTH);
}
